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Tumble Generators

I have been reading info on your site for years now and love your articles. I have however been looking for information on Tumble Generator Valves delete on your site with no luck. Do you have any info on it?

Roger Roomes

We haven’t covered modifying or removing inlet manifold Tumble Generator Valves.

Paper Model Engine

Cool V12 Four-stroke Engine, an unbelievable magnificent paper model.


Injector Plugs

In reference to Replacing Injector Plugs, I think it would be useful to include a hint in the article for readers to note the location of the wires in the old connector and which way they would fit onto the injector to ensure that the original polarity is maintained. Young players learning EFI may not know the difference. Some aftermarket connectors available already come terminated with wires, and those wires may be simply be a black and a red. The new-style connectors are certainly much easier to unlock from the injector should it become necessary later, although clearance in a tight V engine can be an issue. The original design connectors can be a real pain to unlock, maintainers of Nissan SOHC VG30 engines would no doubt sympathise. The term "keyhole surgery" springs to mind.


Assessing Road Surfaces

Just had an idea for a project: a system which could be fitted to a normal car to allow members of the general public to perform quantitative road surface evaluations.

Greg Sullivan

We intend to soon cover a data-logging vertical accelerometer than can be used to assess car ride and road surfaces.

Cylinder-Specific Tuning

Re: article Cylinder-Specific Tuning raises some interesting tangents in the area of modern engine design and controls. It seems the background knowledge has been around for some time, it just takes pressing emissions and fuel consumption factors to bring the tech into general practice.

Before anybody goes berating emissions rules, we should consider the flow-on effects of makers needing to improve the efficiency of their engines to cope with emissions rules. Is it even possible to buy a new car in Australia without DOHC, 4- valves-per and sophisticated EFI? Technology that was once the domain of exotic cars eventually has and does filter down to the humblest shopping trolley.

The reign of the four-stroke piston engine had not ended yet, despite numerous rotary-based ideas. Perhaps when we see computerised individual valve operation, somewhat like big solenoids running the valves, we will see some real jumps in engine efficiency. Wasn't Lucas involved in the development of "Helenoids" (High Energy solenoids) back in the 70's just for that purpose? The promise of tractor valve timing at low speed and race valve timing at high speed is too good to let go. Hell, you wouldn't even need a throttle plate, just reduce the valve timing and lift and/or cut out cylinders entirely.

The now pervasive electronic fuel injection was once considered too complex and expensive for the mass market.

Cylinder filling imbalance was addressed to some extent last century with the advent of aftermarket "scatter grind" cams. Owners of BMC A-series engines might nod in agreement.

Even the humble Nissan SOHC VG30 engine might have had some thought put into it to compensate for wildly disparate exhaust secondary lengths, judging by the way the cam pulleys are indexed to their cams. The VG20 might be the same, not sure about that one.

Back to modern day, I suppose it would not be entirely unfeasible for a high-end car to have wideband sensing in each exhaust runner. The computing power would be trivially cheap when mass produced these days.

The article touched on the concept of spark plug indexing. Perhaps there are grounds for an article on its own there?

By the way, what engine were those cutaway views from in the article pictures?

I have seen the trend away from the toothed rubber timing belt back to the chains which the rubber item widely replaced for a while. It would be interesting to see a story about the evolution of timing chains and what made them find favour again.


Some BMW engines control power with variable valve lift. Not sure what the cutaway engine pics were of - we just had them on file.

Possible HPV Springs?

Please pass on to Mr. Edgar another option: Life Fitness "Lifesprings". They are under their home and commercial treadmill decks and are readily available and cheap.

Larry Morgan
United States

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